7. Eating foods rich in carbohydrates before a race is common among marathon runners,all of them need reliable energy sources for peak performance
of whom need
8.Los Angeles’s freeways,usually busier and more crowded than those of other cities,are clogged almost twenty four hours a day,contributing to the city’s pollution problem.
点评： 首先，无论指代，主谓还是时态，本句没有问题，且又是顺叙，直接用“Los Angeles’s freeways”而不用“the freeways of Los Angeles”，所以是正确的。
9.(常考题：修辞对象)Set in the sixteenth century,modern audiences enjoyed the contemporary opera Galileo Galilei written by Philip Glass.
century,Philip Glass’s contemporary opera Galileo Galilei has enjoyed great success with modern audiences.
点评：注意形容的对象和形容的部分要相邻为好，同时注意顺叙，用“Philip Glass’s contemporary opera”而不是“the contemporary opera Galileo Galilei written by Philip Glass.”
10. Whenever television is denounced by viewers for its violence, they call on the department of standard and practice to take action.
Whenever viewers denounce television for its violence,they call
点评： 这样改使句子十分完整，谁“denounce”?是“viewers”，且viewers call…for practice. 同时还是要强调顺叙，不要用被动态。主语为“viewers”而不是“television”
11. Toward the end of the 1990s,it became clear that Internet-based companies were overvalued in the stock market,since such is the case,their stock prices have dropped considerably in recent years.
and consequently their stock prices have dropped considerabley in recent years
点评：这一类语句表因果。很多错误选项都在后面届一个句子并以“because of that”，“as a result”，“for this reason”。其实都不对。直接用“consequently”顺接表结果。 像“as result”一般中间应用分号隔开。
12. (常考题：转折) Abraham Lincoln is frequently lauded as a successful politician,and his early political career was dominated by a string of lost elections.
Although Abraham Lincoln is frequently lauded as a successful politician,